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CALGARY, Alberta, December 13, 2006, Gran Tierra Energy Inc. (OTC Bulletin Board: GTRE.OB) today announced that the Company has initiated drilling operations in Argentina and is mobilizing three rigs in Colombia as part of a continuous drilling program scheduled through 2007.

Drilling commenced on the Puesto Climaco-2 sidetrack in the Vinalar block in Argentina on November 29. Gran Tierra holds a 50% working interest in this area. The deviated well has reached its planned depth of 3,713 meters, the target reservoir has been penetrated and logging activity has commenced. Results will be evaluated in the coming week. Production facilities associated with the Puesto Climaco field are in place and ready to accommodate additional production from the Puesto Climaco-2 sidetrack immediately if successful.

Also in Argentina, a workover rig is being mobilized to the Ipaguazu field to recomplete the IPX-1 well and re-establish production from this shut-in field. Gran Tierra holds a 100% working interest in the Ipaguazu block. These operations are expected to continue through the month of December.

In Colombia, a drilling rig is being mobilized to drill the Laura-1 prospect in the Talora block in the Middle Magdalena Basin. This well is scheduled to begin drilling in late December and reach target depth in early January 2007. Gran Tierra has a 20% carried working interest in this block.

A second rig is being prepared to move to drill the Caneyes-1 prospect in the adjacent Rio Magdalena block in Colombia in early January, 2007. Gran Tierra currently holds a 100% working interest in this contact area, which is subject to a 30% back-in provision by Ecopetrol, the government petroleum agency, in the event of commerciality. Completion of this well is expected in mid January, 2007.

A third drilling rig is currently being mobilized to drill the Juanambu-1 prospect in the Guayuyaco block in the Putumayo Basin of Colombia. Drilling is expected to commence by January 15, 2007. Gran Tierra's interest in this block is 35% after the Ecopetrol back-in. The rig is planned to be moved to the adjacent Chaza block to drill the Naboyaco-1 prospect in February 2007. Gran Tierra Energy holds a 50% working interest in the Chaza contact area.

Five additional new wells are scheduled to be drilled in Colombia and Argentina over the first three quarters of 2007 by the Company. A significant work-over program is also planned for the year to enhance production from existing wells.

Dana Coffield, President and Chief Executive Officer of Gran Tierra, stated "The onset of simultaneous drilling operations in our two primary operational arenas, Argentina and Colombia, and the imminent expansion of this drilling program in early 2007 puts substance to our dual strategy of acquiring prospective and underdeveloped lands, and adding production through the drill bit."

About Gran Tierra Energy Inc. Gran Tierra Energy, Inc. is an international oil and gas exploration and production company, headquartered in Calgary, Canada, incorporated and traded in the United States and operating in South America. The Company holds interests in producing and prospective properties in Argentina, Colombia and Peru. To date, the Company has pursued a strategy that focuses on establishing a portfolio of producing properties, development and exploration opportunities, through selective acquisitions, to provide a base for future growth. Additional information concerning Gran Tierra is available at www.grantierra.com. Investor inquiries may be directed to [email protected] or 1-800-916-GTRE (4873).

Forward Looking Statements This press release contains 'forward-looking statements' within the meaning of Section 27A of the Securities Act of 1933, as amended, and Section 21E of the Securities Exchange Act of 1934, including without limitation those statements regarding the Company's ability to exploit oil and gas exploration opportunities. These statements are expressed in good faith and based upon a reasonable basis when made, but there can be no assurance that these expectations will be achieved or accomplished. Although the forward-looking statements in this release reflect the good faith judgment of management, forward-looking statements are inherently subject to known and unknown risks and uncertainties that may cause actual results to be materially different from those discussed in these forward-looking statements including, but not limited to, our ability to complete the Company's drilling program for 2007, our ability to discover reserves that may be extracted on a commercially viable basis, difficulties inherent in estimating oil and gas reserves, intense competition in the oil and gas industry, environmental risks, regulatory changes and general economic conditions including the price of oil and gas. Readers are urged not to place undue reliance on these forward-looking statements, which speak only as of the date of this release. We assume no obligation to update any forward-looking statements in order to reflect any event or circumstance that may arise after the date of this release, other than as may be required by applicable law or regulation. Readers are urged to carefully review and consider the various disclosures made by us in the our reports filed with the Securities and Exchange Commission, including those risks set forth in the Company's Annual Report on Form 10-KSB filed on March 10, 2006, as amended, which attempt to advise interested parties of the risks and factors that may affect our business, financial condition, results of operation and cash flows. If one or more of these risks or uncertainties materialize, or if the underlying assumptions prove incorrect, our actual results may vary materially from those expected or projected. We undertake no obligation to update these forward looking statements.